Networking Definitions

This glossary explains the meaning of key words and phrases that information technology (IT) and business professionals use when discussing networking and related software products. You can find additional definitions by visiting WhatIs.com or using the search box below.

  • N

    NIS (Network Information System)

    NIS (Network Information System) is a network naming and administration system for smaller networks that was developed by Sun Microsystems.

  • non-geographic number

    A non-geographic number, also called a virtual number, is a telephone number associated with a country, but not to any single geographic location within that country.

  • nslookup

    nslookup is the name of a program that lets an Internet server administrator or any computer user enter a host name (for example, "whatis.com") and find out the corresponding IP address or domain name system (DNS) record.

  • NVGRE (Network Virtualization using Generic Routing Encapsulation)

    NVGRE (Network Virtualization using Generic Routing Encapsulation) is a network virtualization method that uses encapsulation to create large numbers of virtual LANs (VLANs) for subnets that can extend across dispersed data centers and Layers 2 and 3.

  • What is NetOps? Everything you need to know

    NetOps, also referred to as NetOps 2.0 and NetDevOps, is an approach to networking operations that uses DevOps tools and techniques to make network changes more efficiently and effectively than in the past.

  • What is network virtualization? Everything you need to know

    Network virtualization is a method of combining the available resources in a network to consolidate multiple physical networks, divide a network into segments or create software networks between VMs.

  • O

    OA&M (operations, administration, and management)

    OA&M (operations, administration, and management) is a general term used to describe the costs, tasks involved, or other aspects of operating, administering, and managing something such as a computer network.

  • OF-Config (OpenFlow Configuration and Management Protocol)

    The OpenFlow Management and Configuration Protocol (OF-Config) is a protocol developed under the Open Networking Foundation used to manage physical and virtual switches in an OpenFlow environment.

  • OFDMA (orthogonal frequency-division multiple access)

    Orthogonal frequency-division multiple access (OFDMA) is a feature of Wi-Fi 6 (802.11ax) that allows access points to serve multiple clients at the same time.

  • offline

    Offline is the condition of being capable of but currently not connected to a network of computers or other devices.

  • online

    Online is the condition of being connected to a network of computers or other devices.

  • ONOS (Open Network Operating System)

    ONOS (Open Network Operating System) is an operating system (OS) designed for network service providers to help build carrier-grade software-defined networks architected for high scalability, availability and performance

  • open networking

    Open networking describes a network that uses open standards and commodity hardware.

  • OpenFlow controller

    An OpenFlow controller is an application that manages flow control in a software-defined networking (SDN) environment.

  • OpenFlow switch

    An OpenFlow switch is a software program or hardware device that forwards packets in a software-defined networking (SDN) environment.

  • OpenStack Neutron (formerly called Quantum)

    OpenStack Neutron is a cloud networking controller and a networking-as-a-service project within the OpenStack cloud computing initiative.

  • operational support system (OSS)

    An operational support system (OSS) is a set of programs that help a communications service provider monitor, control, analyze and manage a telephone or computer network.

  • optical line terminal (OLT)

    An optical line terminal (OLT) is a device that is located at the service provider's central office and is the endpoint of a passive optical network (PON).

  • optical network (photonic network)

    An optical (photonic) network transmits information as optical rather than electronic signals: It uses light, not electrical currents, to convey data.

  • optoelectronics

    Optoelectronics is a branch of electronics that overlaps with physics.

  • optoisolator (optical coupler or optocoupler)

    An optoisolator (also known as an optical coupler, photocoupler, optocoupler) is a semiconductor device that transfers an electrical signal between isolated circuits using light.

  • orthogonal frequency-division multiplexing (OFDM)

    Orthogonal frequency-division multiplexing (OFDM) is a method of data transmission where a single information stream is split among several closely spaced narrowband subchannel frequencies instead of a single wideband channel frequency.

  • OSGi (Open Service Gateway Initiative)

    The OSGi (Open Service Gateway Initiative) specification is a Java framework for developing and deploying modular software programs and libraries.

  • OSI model (Open Systems Interconnection)

    OSI (Open Systems Interconnection) is a reference model for how applications communicate over a network.

  • OSPF (Open Shortest Path First)

    The OSPF router protocol is used to find the best path for packets as they pass through a set of connected networks. OSPF is one of several Interior Gateway Protocols that replaces the Routing Information Protocol (RIP), an older routing protocol that is installed in many of today's corporate networks.

  • over-the-top (OTT)

    Over-the-top (OTT) is networking lingo that describes the delivery of content, services or applications over the internet.

  • overlay network

    An overlay network is a virtual or logical network that is created on top of an existing physical network.

  • OVSDB (Open vSwitch Database Management Protocol)

    The Open vSwitch Database Management Protocol (OVSDB) is an OpenFlow configuration protocol that is designed to manage Open vSwitch implementations.

  • P

    packet filtering

    On the Internet, packet filtering is the process of passing or blocking packets at a network interface based on source and destination addresses, ports, or protocols.

  • packet loss

    Packet loss is when one or more transmitted data packets fail to arrive at their destination.

  • packet-switched

    Packet-switched describes the type of network in which relatively small units of data called packets are routed through a network based on the destination address contained within each packet.

  • passive optical network (PON)

    A passive optical network (PON) is a system commonly used by telecommunications network providers that brings fiber optic cabling and signals all or most of the way to the end user.

  • patch panel

    A patch panel in a local area network (LAN) is a mounted hardware assembly that contains ports that are used to connect and manage incoming and outgoing LAN cables.

  • peer-to-peer (P2P)

    Peer-to-peer (P2P) is a decentralized communications model in which each party has the same capabilities and either party can initiate a communication session.

  • permanent virtual circuit (PVC)

    A permanent virtual circuit (PVC) is a software-defined logical connection in a network such as a frame relay network.

  • phase-locked loop (PLL)

    A phase-locked loop (PLL) is an electronic circuit with a voltage or voltage-driven oscillator that constantly adjusts to match the frequency of an input signal.

  • physical layer

    Located at the lowest layer of the Open Systems Interconnection (OSI) communications model, the physical layer's function is to transport data using electrical, mechanical or procedural interfaces.

  • ping

    A ping (Packet Internet or Inter-Network Groper) is a basic internet program that enables a user to test and verify if a particular destination Internet Protocol (IP) address exists and can accept requests in computer network administration.

  • ping sweep (ICMP sweep)

    A ping sweep (also known as an ICMP sweep) is a basic network scanning technique used to determine which of a range of IP addresses map to live hosts (computers).

  • Plain Old Telephone Service (POTS)

    Plain Old Telephone Service (POTS) refers to the traditional, analog voice transmission phone system implemented over physical copper wires (twisted pair).

  • plesiochronous

    Plesiochronous (pronounced plee-see-AH-krun-us, from Greek plesos, meaning close, and chronos, meaning time) is an adjective that describes operations that are almost, but not quite, in synchronization - in other words, almost synchronous.

  • point-of-presence (POP)

    On the Internet, a point-of-presence (POP) is an access point from one place to the rest of the Internet.

  • Point-to-Point Protocol (PPP)

    Point-to-Point Protocol (PPP) refers to a suite of computer communication protocols that provide a standard way to transport multiprotocol data over point-to-point links.

  • Point-to-Point Protocol over Ethernet (PPPoE)

    Point-to-Point Protocol over Ethernet (PPPoE) is a network protocol that facilitates communication between network endpoints.

  • poison reverse

    In a computer network that uses the Routing Information Protocol (RIP) or other distance vector routing protocol, poison reverse is a loop avoidance process.

  • policy-based networking

    Policy-based networking is the management of a network so that various kinds of traffic - data, voice, and video - get the priority of availability and bandwidth needed to serve the network's users effectively.

  • port

    A port in computing has three main uses, each as a type of receptacle in networking, computer hardware and software.

  • port 80

    On a Web server or Hypertext Transfer Protocol daemon, port 80 is the port that the server "listens to" or expects to receive from a Web client, assuming that the default was taken when the server was configured or set up.

  • Port Address Translation (PAT)

    Port Address Translation (PAT), is an extension to network address translation (NAT) that permits multiple devices on a local area network (LAN) to be mapped to a single public IP address. The goal of PAT is to conserve IP addresses.

  • port mirroring (roving analysis port)

    Port mirroring is an approach to monitoring network traffic that involves forwarding a copy of each packet from one network switch port to another.

  • port number

    Port number is a way to identify a specific process to which an internet or other network message is to be forwarded when it arrives at a server.

  • Power over Ethernet (PoE)

    Power over Ethernet (PoE) is a technology for implementing wired Ethernet local area networks (LANs) that enables the electrical current necessary for operating each device to be carried by Ethernet data cables instead of standard electrical power cords and wiring.

  • POX

    POX is an open source development platform for Python-based software-defined networking (SDN) control applications, such as OpenFlow SDN controllers.

  • preboot execution environment (PXE)

    Preboot execution environment (PXE), pronounced pixie, is a set of standards that enables a computer to load an operating system (OS) over a network connection.

  • presentation layer

    Residing at Layer 6 of the Open Systems Interconnection (OSI) communications model, the presentation layer ensures that the communications that pass through it are in the appropriate form for the recipient application.

  • private automatic branch exchange (PABX)

    A private automatic branch exchange (PABX) is an automatic telephone switching system within a private enterprise.

  • programmable network (network programmability)

    A programmable network is one in which the behavior of network devices and flow control is handled by software that operates independently of network hardware.

  • propagation delay

    Propagation delay is the amount of time required for a signal to be received after it has been sent; it is caused by the time it takes for the signal to travel through a medium.

  • protocol data unit (PDU)

    In networking, a protocol data unit is the basic unit of exchange between entities that communicate using a specified networking protocol.

  • PSTN (public switched telephone network)

    The public switched telephone network, or PSTN, is the world's collection of interconnected voice-oriented public telephone networks.

  • pulse code modulation (PCM)

    Pulse code modulation (PCM) is a digitalscheme for transmitting analogdata.

  • Q

    QAM (quadrature amplitude modulation)

    QAM (quadrature amplitude modulation) is a method of combining two amplitude modulation (AM) signals into a single channel.

  • queries-per-second (QPS)

    Queries-per-second (QPS) (or the query-per-second rate) is a measure of how much traffic a particular query server is handling at a given time.

  • R

    radio access network (RAN)

    A radio access network (RAN) is a major component of a wireless telecommunications system that connects individual devices to other parts of a network through a radio link.

  • radio frequency (RF, rf)

    Radio frequency (RF) is a measurement representing the oscillation rate of electromagnetic radiation spectrum, or electromagnetic radio waves, from frequencies ranging from 300 GHz to as low as 9 kHz.

  • Real-time Transport Protocol (RTP)

    Real-time Transport Protocol (RTP) is a network standard designed for transmitting audio or video data that is optimized for consistent delivery of live data.

  • registered port numbers

    The registered port numbers are the port numbers that companies and other users register with the Internet Corporation for Assigned Names and Numbers (ICANN) for use by the applications that communicate using the Internet's Transmission Control Protocol (TCP) or the User Datagram Protocol (UDP).

  • repeater

    In digital communication systems, a repeater is a device that receives a digital signal on an electromagnetic or optical transmission medium and regenerates the signal along the next leg of the medium.

  • response time

    According to the IBM Dictionary of Computing (which cites International Organization for Standardization Information Technology Vocabulary as the source), response time is: The elapsed time between the end of an inquiry or demand on a computer system and the beginning of a response; for example, the length of the time between an indication of the end of an inquiry and the display of the first character of the response at a user terminal.

  • Reverse Address Resolution Protocol (RARP)

    Reverse Address Resolution Protocol (RARP) is a protocol a physical machine in a local area network (LAN) can use to request its IP address.

  • reverse Telnet (direct Telnet)

    Reverse Telnet (sometimes called direct Telnet) is the initiation of a Telnet session from a computer system to one of its remote users.

  • ROADM (reconfigurable optical add-drop multiplexer)

    An ROADM (reconfigurable optical add-drop multiplexer) is a device that can add, block, pass or redirect modulated infrared (IR) and visible light beams of various wavelengths in a fiber optic network. ... (Continued)

  • round-trip time (RTT)

    Round-trip time (RTT), also called round-trip delay, is the time required for a signal pulse or packet to travel from a specific source to a specific destination and back again...(Continued)

  • route summarization (route aggregation)

    Route summarization -- also known as route aggregation -- is a method to minimize the number of routing tables in an Internet Protocol (IP) network.

  • router

    A router is a physical or virtual appliance that passes information between two or more packet-switched computer networks.

  • Routing Information Protocol (RIP)

    Routing Information Protocol (RIP) is a distance vector protocol that uses hop count as its primary metric.

  • routing table

    A routing table is a set of rules, often viewed in table format, that is used to determine where data packets traveling over an Internet Protocol (IP) network will be directed.

  • RS-232C

    RS-232C is a long-established standard ("C" is the current version) that describes the physical interface and protocol for relatively low-speed serial data communication between computers and related devices.

  • RSVP (Resource Reservation Protocol)

    RSVP (Resource Reservation Protocol) is a set of communication rules that allows channels or paths on the Internet to be reserved for the multicast (one source to many receivers) transmission of video and other high-bandwidth messages.

  • runbook

    Runbooks are a set of standardized written procedures for completing repetitive IT processes within a company.

  • runt

    In networks, a runt is a packet that is too small.

  • S

    satellite news gathering (SNG)

    Satellite news gathering (SNG) is the use of mobile communications equipment for the purpose of worldwide newscasting.

  • SD-branch

    SD-branch is a single, automated, centrally managed software-centric platform that replaces or supplements an existing branch network architecture.

  • SD-WAN (software-defined WAN)

    Software-defined WAN (SD-WAN) is technology that uses software-defined networking (SDN) concepts to distribute network traffic across a wide area network (WAN).

  • SDN application (software-defined networking application)

    An SDN application is a software program designed to perform a task in a software-defined networking (SDN) environment. SDN applications can replace and expand upon functions that are implemented through firmware in hardware devices in a conventional networking environment.

  • SDN controller (software-defined networking controller)

    An SDN controller is an application in a software-defined networking (SDN) architecture that manages flow control for improved network management and application performance.

  • SDN overlay (software defined networking overlay)

    An SDN overlay is a deployment method for network virtualization and software-defined networking (SDN) that involves running a logically separate network or network component on top of existing infrastructure.

  • Secure Access Service Edge (SASE)

    Secure Access Service Edge, also known as SASE -- pronounced 'sassy' -- is a cloud architecture that bundles network and security solutions together and delivers them as a unified cloud service.

  • Seebeck effect

    The Seebeck effect is a phenomenon in which a temperature difference between two dissimilar electrical conductors or semiconductors produces a voltage difference between the two substances.

  • serial digital interface (SDI)

    Serial digital interface (SDI) is a standard for digital video and audio transmission over coaxial or fiber optic cabling.

  • Server Message Block protocol (SMB protocol)

    The Server Message Block protocol (SMB protocol) is a client-server communication protocol used for sharing access to files, printers, serial ports and other resources on a network.

  • Service Profile Identifier (SPID)

    In telecommunications, a Service Profile Identifier (SPID) is a number assigned by a phone company to a terminal on an Integrated Services Digital Network (ISDN) B-channel.

  • session border controller (SBC)

    A session border controller (SBC) is a dedicated hardware device or software application that governs the manner in which phone calls are initiated, conducted and terminated on a voice over Internet Protocol (VoIP) network.

  • Session layer

    In the Open Systems Interconnection (OSI) communications model, the session layer resides at Layer 5 and manages the setup and teardown of the association between two communicating endpoints.

  • session-based routing

    Session-based routing is a type of routing architecture that is application-centric and designed to route entire sessions instead of individual packets.

  • Shannon's Law

    Shannon's Law, formulated by Claude Shannon, a mathematician who helped build the foundations for the modern computer, is a statement in information theory that expresses the maximum possible data speed that can be obtained in a data channel.

  • shielded twisted pair (STP)

    Shielded twisted pair (STP) is a special kind of copper telephone and local area network (LAN) wiring used in some business installations.

  • signal

    In electronics, a signal is an electric current or electromagnetic field used to convey data from one place to another.

  • signal-to-noise ratio (S/N or SNR)

    In analog and digital communications, a signal-to-noise ratio, often written S/N or SNR, is a measure of the strength of the desired signal relative to background noise (undesired signal).

  • Signaling System 7 (SS7)

    Signaling System 7 (SS7) is an international telecommunication protocol standard that defines how the network elements in a public switched telephone network (PSTN) exchange information and control signals.

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